Combustion system and safety device therefor



Jan. 10, 1928.

L. L. SCOTT COMBUSTION SYSTEM AND SAFETY DEVICE THEREFOR 2 Sheets-Sheet 1 Original Filed Feb. 4, 1925 III/Jam. I

Jan. 10, 1928.

L. L. SCOTT COMBUSTION sYsTEM AND SAFETY DEVICE THEREFOR Original Filed Feb. 4, 1925 2 Sheets-Sheet 2 IN VEN TOR.

ATTORNEY5 Patented J an. i It), 1928.

T OFFICE.

LEWIS I. SCOTT, OF ST. LOUIS, MISSOURI.

COMBUSTION SYSTEM AND SAFETY DEVICE THEREFOR.

Continuation 6: application Serial No. 6,909, filed February}, 1925. This application filed aui ae, 1e27, Serial No. 209,287.

This invention relates to combustion systems and particularlyto safety devices especially adapted for use in oil burning apparatus. This application is a continuation of my pending application, Serial N 0. 6,909, filed February 4th, 1925.

As a rule, the electrical circults for operating the various elements in 011 burning apparatus are controlled by safety (lQVICGS tO function and render the system inoperative upon a. circuit being established or closed by the device in the event the fuel supplied to the combustion chamber is not properly combusted when the system is initially put in 5 operation. In arrangements such as these,

that is, in arrangements which rely upon the making of a circuit, there is, necessarily, the danger of the safety device failing to function properly, especially if the contacts of the device become dirty or otherwise get in a condition that prevents them making the proper electrical connection or contact. The present invention, therefore, has one of its objects the provision of a circuit arrangement and a safety device whose contacts are normally closed, and must be so, to allow initial operation and combustion, but whose contacts must be open by conditions caused by combustion of the fuel wltlnn a. short period of time after initial combustion takes place in order that the system may continue in operation, the system being rendered inoperative in the event said contacts remain closed for a predetermined time after the system is started. In other words. the contacts of the safety device must be closed before the system is started but after the system is started the contacts must be open, or, otherwise, the safety feature Wlll function. to render the entire system inoperative. With such an arrangement as this, the system cannot be placed in operation should the safety contacts be fouled as the making of the circuits through those con-- tacts' is a prerequisite to the initial operation of the system, and once the system 18 started the safety device, which serves to protect against improper initial combustion,

Will function to render the system inoperative, not by making a contact, but by breaking one. i

The invention also contemplates a combustion system wherein the operationof the burner is controlled by a thermostat located at some remote point, for-instance, a room in the building, the arrangement being such that the contacts of the thermostat engage at a predetermined temperature to initiate combustion but are disengaged entirely at a higher temperature to render the system inoperative. Hence, after the system has been placed in operation and the room theremostat is relied upon to stop combustion when the temperature in the room reaches the higher degree there is no necessity of the thermostat completing a circuit because of the cessation of operation, as in other devices; hence, there is no liability of the thermostat failing to operate should the contacts thereof become fouled. To cause a. cessation of operation the thermostat breaks a circuit only and the fact is that, if any one of the thermostat contacts failed to function properly for any reason the system cannot be put into operation. These are the primary objects of the invention, butthere are other minor novel details and arrangements which will appear in the following description of the system wherein the invention is illustrated as applied to an oil burner. It will be understood, however, that the invention is not limited to a system of the oil burner type except as expressed or called for in the claims appended to the ensuing specification.

In the accompanying drawings,

Figure 1 illustrates more or less diagrammatically the preferred arrangement of the circuits as contemplated by the present invention.

Fig.- 2 is a detail thermostat switch. r

Fig. 3 is a. detail front view of the safety switch shown in Fig. 1.

Fig. 4 isa detail view of a modified conend view of the stack tact arrangementlfor the stack thermostat,

this form being used where quick action and a nicety of time is desired.

Fig. 5 is a sectional view on the line 5-5 of Fig. 4:.

In the accompanying drawings, the electric motor indicated at 1 operates a fan wheel 2 and a fuel pump 3, the wheel 2 being mounted ina housing 4 connected to a pipe 5, the

f cal contacts at one end interior of which constitutes the combustion chamber. A suction pipe 6 connected to the pump 3 communicates with a fuel tank, not shown, and pump 3 is connected by a discharge pipe 7 to a fuel spray nozzle 8 in the combustion chamber. When the system is initially placed in operation the motor actuating pump 3 feeds fuel through the pipe 7 to the nozzle 8 at which point it is ordinarily ignited by a spark created by the spark plug 9 projecting through the side of pipe 5. Air from the air blower is mixed with the fuel spray to give a good combustible mixture and the ignited mixture is conducted through pipe to a heat absorbing medium which need not be shown.

Current for motor 1 is taken from any source such as a 110-volt power circuit through what for convenience might be termed the main feed wires 10. There the burner is used for heating dwelling places, it is customary to use a room thermostat 11 that automatically controls the operation of the burner in suchwise that the burner will be put into operation when the temperature in the room goes down to a certain degree and is rendered inoperative after sufficient heat has been generated to raise the temperature in the room to a predetermined higher degree. Current going through the motor 1 traverses a circuit in which there is a switch 12 such as a mercury switch con sisting of a glass tube containing a small amount of mercury and having two electriof the tube. The wire 13 running from one of the contacts in the mercury tube connects to one of the wires and the wire 14 connecting with the other contact in the mercury tube connects to motor '1 through a wire 15 and to transformer 16 through the wire 17. The other side of the transformer 16 is connected by wire 18 to the power line and a wire 19 runs from the power line to motor 1 as well as to another transformer 20. The other side of the power line is connected directly to transformer 20 by a wire 21. Thus it will be seen that transformer 20 is connected directly to the main power line and the motor 1 and transformer 16 is connected to the main power line through the mercury switch 12.

Preferably the mercury switch tube is carried by a clip 22 connected at one end to the core of a solenoid magnet and when the solenoid is energized the end of the clip connected to the solenoid will be raised upwardly to tilt theopposite end of the tube, as shown, so that the mercury within the tube will bridge the gap between wires 13, 14, closing the circuit to motor 1 and transformer 16. At the same time the wires 13, 14, are connected by the mercury in the mercury tube, it is desired to establish a second circuit. For this purpose the clip has a projecting arm 26 which extends through a slot in a spring 27 and when the tube is in the position shown the spring 27 is released so that it moves to the left as illustrated and makes contact with a post 28, the purpose of which will later appear. When the current is shut off in the solenoid 24 solenoid core 25 will move downward and restore the mercury tube to such a position that the mercury will run back to the opposite end of the tube and thereby disconnect the contacts of wires 13, 14, within the tube, this resulting in a breakingof the circuit to motor 1 and transformer 16. At the same time contacts 27 and 28 will also be separated.

One end of the coil of the solenoid 24 is connected to the low voltage side of the transformer 20 by a wire 29 which leads fromthe solenoid to a safety switch whose terminals are indicated at 51 and 31 and a wire 32 which runs from contact 31 of the switch to the transformer. The other end of the solenoid coil runs by awire 33'to a contact member 34 of the room thermostat 11 and from contact 35 of the thermostat to ground by way of the wire 36. And in order for the circuitfrom wire 36 to be completed through the transformer wire 37 from sai transformer it has a branch 38 which leads to contact member 39 of the stack thermostat switch whose other contact member 40 has connected thereto a wire 41 which runs through the secondary coil 42 of the-transformer 16 and from thence by wire 43 and coil 44 to ground. This circuit, for convenience, might be termed the main operating circuit for the solenoid.

The ignition circuit for the spark plug 9 contains the usual present day type of spark coil 45 from which extends the wire 46 for supplying current to the plug from the coil 42 of transformer 16. The wire 41 from coil 42 of transformer 16 completes the circuit to the spark coil 45 through the contacts 39 and 40, wire 38, wire 47, through contacts 27, 28. heretofore described as having been operated by tilting of the mercury tube clip, thence by by way of wire 48 to the room thern'iostat 11 and from contact 35 of the thermostat to ground by way of wire 36. Coil 44 in the main solenoid operating circuit is adapted to generate sufficient heat to effect the piece of thermostatic metal 49 as the current passes through the solenoid operating circuit. The thermostatic metal 49 has one end secured to a point 50 and its other end, upon the metal-being heated to the proper temperature, will move to one side, the left side in the accompanying drawing, and will, upon sufficient movement in that direction. effect the breaking of the contacts 30,31, in the manner somewhat similar to the electrically heated thermo-switches shown in my pending applications Serial Nos. 57 8,7 ()9. and 581,540. While various forms of switches of this type might be utilized that illustrated in the present instant comprises a slotted post 51 secured to a switch board, (not shown) and two U-shaped members 52, 53 (see Fig. 3) are held against said post by a spring 54. A pin 55 secured to the outer extremity of the U-shaped piece 53 contacts with the movable end of the thermostatic strip 49 whereby the U-shaped members, which form part of the circuit, may be moved by deflection of said thermostatic member. To limit the range of movement of the members 52, 53, stop members are provided such as pins 56, 57 and 58. In the drawings, contacts 30, 31, are shown as closed but under certain conditions the thermostatic strip 49 will heat up and will act on member 55 to move the free end of U-shaped piece 53 to the left until it moves far enough pastcenter to cause spring 54 to act upon the other'U-shaped member 52 and move the outer extremity of that member-to the left to separate the contact members 30, 31. In the absence of combustion in the combustion chamber contacts 39, 40 are closed so that upon current flowing through wires 19, 21, to the transformer 20, the main solenoid operating circuit will-be complete and the solenoid energized. Mercury tube 12 will be tilted-and the circuit to motor 1 completed, the spark circuit completed, and the circuit which will be called the secondary or parallel solenoid circuit also completed.

This secondary or parallel solenoid circuit,

runs from transformer. through wires 37, 47, to switch contacts 27, 28, wire 48 to the room thermostat, from contact 34 of the thermostat through wire 33 to the solenoid, from the solenoid by wire 29 to post 51 of the switch and from contact 31 of the switch by wire 32 back to the secondary coil of the transformer 20. It will thus be seen that both of the solenoid operating circuits may be interrupted by operation of the switch members 52, 53 by heating up of coil 44.

The purpose of this will appear later.

As will be seen the stack thermostat switch comprising contacts 39, is included in both the spark circuit and the main solenoid circuit and for this reason contacts 39, 40 must be engaged in order that the system may be initially placed in operation. Upon the system being placed in operation, contacts'39, 40 will remain closed if the fuel is not properly combusted, but if proper initial combustion takes place said contacts are adapted to be separated by some suitable means. Such means may comprise a thermostatic arrangement such as shown in Figs. 1 and 2 wherein there is a coiled strip of thermostatic metal 59 having one of its ends secured to a plug 60 within-the combustion .chamber and its opposite end secured to a small shaft 61 which operates or moves contact 40 away from contact 39 through memcuit to the solenoid 25 but also the circuit 7 through spark coil 45 and the thermo-coil 44. The time required to open contacts 39, 4O depends on how near the thermo-metal 59 is located to nozzle 8 but it is usually set to open said contacts in from one to two minutes. The thermostatic strip 49 for separating contacts 30, 31 is set to break said contacts in the event a current is maintained through the thermo-coil 44 for four minutes and by 7 39, 40 and 30, 31 the current to the coil 44 will be cut off by the opening of contacts 39, 40 upon the normal igniting of the fuel before the coil 44 can effect a separation of contacts 30, 31. supplied to the combustion chamber is not initially ignited contacts 39, 40 will not be separated due to the absence of heat in the chamber, with the result that current will continue to flow through the thermo-coil 44 for the period necessary to cause the disen-J gagement of contacts 30, 31 with the result that both of the solenoid operating circuits will be broken and that mercury tube will be actuated to break the connection between 0 wires 13, 14. This renders the entire system inoperative and g ves notice to the attendant that an investigation of the operating parts should be made. It will be understood that the attendant, after rectifying any disorders, I

must manually restore contacts 30, 31, before the system can again be placed in operation.

combustion has once been started the heat of the flame within the chamber continues to ignite the fuel supplied thereto after the circuit to thespark plug has been broken b disengageigent of contacts 39, 40.

With fil -arrangement such as this it will be seen that control of the system, insofar as is not true of those safety devices wherein control of the system is had by making the 195 circuit because in such systems as those the safety device will fail to put the system out of operation in the event its contacts become dirty or foul.

The purpose for the circuit heretofore 0 the path of the incoming 70 7 so timing the breaking of contacts 85 But, in the event the fuel 90' It will also'be understood that after increases the degree of 1 with contactmember 40* I A wire 74 leading-from wire 36 and of the main operating circuit for the the contact members 30,

,of the thermostat strip termed the secondary operating circuit of thesolenoid will now be apparent. Upon proper initial combustion contacts 39, 40 will be separated, resulting in the breaking solenoid, but the secondary circuit for energizing the solenoid will not be broken unless 31 of the switch before referred to are disengaged.

In the room thermostat 11 the same principle of relying upon the breaking of the circuit to render the system inoperative, instead of relying upon the making of. a cir' cuit to do so, is utilized, the arrangement being such that the system cannot be placed in operation unless contacts 65, 35, and 66, 34, are in engagement. This being true, the system is rendered inoperative in the event said contacts are not properly engaged with one another and it is not necessary for any circuit to be made to render the system inoperative. IIence, if the contacts become dirty or foul there will be absolutely no danger of the thermostat failing. to render the system inoperative. In actual practice it has been found desirable to give contact as a slight lead over contact so that it contacts with its cooperating contact 66, first, but the burner will not start until contact 35 engages contact because until this takes place there will be no spark to initiate combustion. When the room has reached a predetermined temperature contact 65 will leave contact 35 first, but the burner will not shut ofl until contact 66 leaves contact 34 as it is this plan ofcontacts that controls the supply of fuel which at that time is being ignited by the flame present in the com bustion chamber. The thermostat is, of course, arranged to complete the necessary circuits upon the temperature reaching a predetermined degree and to break said circuits the temperature in the room reaching a predetermined higher degree.

While thermostat 59, illustrated in Figs. 1 and 3 have been found to work satisfactorily in practically all respects, the arrangements shown in Figs. 4 and 5 may be used in lieu thereof in instances where a niccty of timing and quick action is wanted. In this form of thermostat the thermostatic strip 70 is positioned in proximity to a small slot in the wall of the stack 71, one end being secured to a shield 72 and the other'end thereof being adapted to engage a contact member 40 carried on a'spring member to which the wire ell is connected. The other contact member 39 to which wire 38 is connected is.

properly secured on an insulated base73 it and the free end of the thermostatic strip.

shield 7 2 are grounded as indicated in Fi l. This form of thermostat is, in fact. pre- 'high temperatures positioned between the ferred to that shown in the diagram'matical lay-out for the reason that it will take care of certain possible conditions that might arise. For instance, assuming that the burner is not burning and that the tempera ture is beginning to drop so that the contact 66 on the room thermostat has been made and contact 65 is very close to being made and someone jars the room thermostat so as to momentarily cause contact 65 to close and then open, this condition might cause the solenoid to function and start up the burner but as the contact 65 must be closed in order to get a spark at the spark plug there will be no spark and the result would be undesirabler This condition is taken care of by having the contact 40* positioned intermediate contact 39 and the free end of thermostat strip 70. Other advantages of this thermostat arrangement are as follows: A true thermostatic metal may be used on the exterior of the stack whereas an expanding rod would have to be used if the member were located within the stack because the in the stack would soon ruin the action of a thermostatic metal. Furthermore, the time element required with an expanding rod is undesirable, the contraction of the rod, after the fire has been shut off, being entirely too slow as con'ipared with the action of the thermostatic metal which will'return the'contacts to closed position very quickly, ing augmented by the fact that cold air is sucked through the shield 72 and over the thermostat metal through the slot in the stack 75. I

I claim:

1. In a combustion system, the combination of a combustion chamber, means for feeding fuel thereto including an electric motor, means for igniting said fuel, an electric circuit for said motor including a switch. means for maintaining said switch closed including an electric circuit having a normally-closed safety switch therein, and means for opening said safety switch comprising an electric circuit and a switch therein responsive to combustion conditions and closed in the absence of and open in the presence of combustion in said combustion chamber.

2. An electricalcontrol system for liquid fuel burners comprising a burner motor, a motor circuit in which said motor is connected, a main switch in said motor circuit which opens automatically when released, electrically operated means for closing the main switch and holding it closed, a secondary circuit including said switch-closing means and a normally-closed safety switch, and a safety circuit including a timed devicefor opening said safety switch and a switch responsive to combustion conditions, said lastmentioned switch being closed in Chi " combustion.

3. An electrical control system for liquid fuel burners comprising a burner motor, a main circuit in which said burner is connected, a switch for controlling the main circuit, aisolenoid for operating saidswitch, the latter being maintained closed when the solenoid is energized and opening automatically when it is de-energized, a secondary circuit including said solenoid, a source of current, and a normally closed safety switch, time'd means for automatically opening said safety switch at the end of a predetermined interval after the energizing of said solenoid, said means being ineffective to close the switch, and means for rendering said timed means inoperative upon the establishment of combustion.

4. In a combustion system con'lprising'a combustion chamber, means for supplying fuel to said chamber, and means for igniting said fuel, an electrical control system including a main circuit, a main switch in said circuit, a second circuit controlling the closing of said main switch, a normally-closed safety switch in said second circuit, and means, including a circuit closer responsive to combustion conditions and closed in the absence of and open in the presence of combustion in the combustion chamber, for opening said safety switch automatically and thereby cutting off the fuel to the combustion chamber upon initial failure of combustion within a predetermined time after said main switch has been closed. r

5. In a combustion system comprising a combustion chamber, means for supplying fuel to said chamber, and means for igniting said fuel, an electrical control system including a main electric circuit, a main switch in said circuit, a secondary circuit controlling the closing of said main switch, a normally closed safety switch in said secondary circuit, and means for automatically opening said safety switch upon initial failure of combustion within a predetermined time after said main switch has been closed, thereby causing the opening of the main switch, said means being ineffective to close the safety switch. 6. An electrical control systemfor liquid fuel burners comprising electrically operated means for projecting fuel into a zone of ignition, means for igniting said fuel, a main electric circuit including said fuel projecting means, a main switch in said circuit, means for automatically opening said main switch including a normally-closed safety switch,

' means for automatically opening said safety switch, thereby causing the opening of the main switch including an electric circuit and a heating coil therein, said means being timed to open said safety switch at the end of a redetermined interval after the closing of he main switch, and said circu t including theheating coil being closed upon the closing of the main switch, andi'ineans for breaking said circuitincluding .the heatcoil, upon the initiation of combustion. a.

7. An electrical control system for liquid fuel burners comprising electrically operated meansfor projecting fuel into a zone of ignition, means for igniting said fuel, a main electric circuit including said fuel projecting means, and safety means for automatically breaking said main circuit upon the failure of combustion, said safety means including a secondary circuit and means, including a circuit closer responsive to combustion conditions and closed in the absence of and open in the presence of combustion in the combustion chamber, for automatically breaking said secondary circuit and thereby breaking the main circuit at the end of a predetermined interval after the closing of the main circuit, in the absence of combustion.

8. In a combustion system comprising a combustion chamber, means for supplying fuel to said chamber and means for igniting said fuel, an electrical control system, including a main circuit, a main switch in said circuit, a second circuit controlling the closing of the main switch, a normally closed safety switch in said second circuit and means for opening said safety switch automatically, a switch, responsive to combustion conditions, controlling said second circuit, which switch is closed in the absence of and open in the presence of combustion in the combustion chamber, said last named switch also controlling the normal starting of the fuel supply means.

9. In a combustion system comprising a combustion chamber, means for supplying fuel thereto, and means for igniting said fuel, an electrical control system comprising a main circuit including said fuel projecting means, safety means for automatically breakng said main circuit upon the failure of combustion, said safety means including a second circuit and a normally closed safety switch therein, means for automatically opening .said safety switch, and a switch responsive to combustion conditions, closed in the absence of and open in the presence of combustion in the combustion chamber, said last named switch controlling the automatic opening of the safety switch and the closing of the main circuit in normal starting of the fuel supply means.

10. In a combustion system comprising acombustion chamber, means for supplying fuel to said chamber and means for igniting said fuel, an electrical control system, including a main circuit, a main switch in said circuit, a second circuit controlling the closing of the main switch, a normally closed safety switch in said second circuit and means for opening said safety switch automatically, a switch responsive to combustion conditions controlling said second circuit, which switch is closed in the'absence of and open in the presence of combustion in the presence of combustion in the combustion chamber, a second switch in the second cir cuit which is automatically closed at the time the main switch operates to close, said second switch being a parallel circuit to the switch which isv responsive to combustion conditions, said switch which is responsive to combustion conditions also controlling the normal starting of the fuel supply means.'

for the purpose of establishing LEWIS L 30011, a 

